I had a toy called the SST - it consisted of a little vehicle that was revved up by pulling a plastic rip cord through a central wheel, and then letting it go down the street. If you didn't position your hand holding the vehicle just right, you could get a nasty friction burn between your thumb and forefinger.
My Stingray, the bike of choice then, had to be redesigned in the following years after my model. It featured a gear shift on the center bar. Apparently it was in just the wrong position if a boy should slip forward and end up straddling the gear shift. Happily, that never happened to me!
Most kids at the time played with gunpowder - in the form of cap guns - and the rolls of ammunition, which consisted of bits of gunpowder encased in little paper bubbles The roll would be fed through a cap gun, which would set each off with a loud bang and a puff of smoke. Of course, after a while, we just took the rolls of ammunition, set them down on the curb, and just set them off by pounding rocks on them. All we wanted was the boom. It's a good thing it didn't occur to us to perform a little surgery and collect all the little drops of gunpowder into something more potent.
Of course, it wasn't always the toy that was dangerous. At one time, I attempted to take apart an old radio - while it was plugged into the wall (actually, it was plugged into the side of the house outside, where I could go about my mischief undisturbed). As a result, I remember precisely where I was when I learned, with a jolt, about the dangers of electrocution. Some years later in junior, not surprisingly, I earned my single worst shop class grade in the Electrical class.